The disclosure of Japanese Patent Application No. HEI 11-322371 filed on Nov. 12, 1999 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a fuel evaporative emission controller for preventing an evaporation gas in an automobile fuel tank from emitting into the air.
2. Description of Related Art
An automobile fuel tank is provided with valves, for example, a fuel-level sensing valve for closing a vent line when the tank is filled up with the fuel, a tank pressure control valve for maintaining the pressure in the fuel tank always at a predetermined value, a fuel cut valve for closing an evaporate line upon tilting and overturning of the automobile so as to prevent the fuel from flowing out through the evaporate line.
In a fuel evaporative emission controller as one related art shown in FIG. 17, a valve structure 4 formed by integrating a fuel-level sensing valve 2 and a fuel cut valve 3 is mounted to a fuel tank 1. The valve structure 4 is provided with a vent line 5 and an evaporate line 6, each of which leads to a canister 7.
The vent line 5 is provided with a diaphragm valve 8 that opens and closes the vent line 5 according to the pressure upon fuelling. The evaporate line 6 is provided with a tank pressure control valve 9 that opens and closes the evaporate line 6 according to the pressure in the fuel tank 1.
The tank pressure control valve 9 includes a mechanical valve that opens and closes according to a mechanically detected pressure (by means of fluid) in the fuel tank 1, and an electromagnetic valve that opens and closes according to an electrically detected pressure in the fuel tank 1. The electromagnetic valve is actuated by a pressure sensor 10 attached to the fuel tank 1. The pressure sensor 10 detects a pressure in the fuel tank 1.
Upon increase in the fuel-gas pressure in the fuel tank 1 at fuelling, the fuel gas flows through a valve seat 2A of the fuel-level sensing valve 2 provided in the valve structure 4, and opens the diaphragm valve 8 to enter the vent line 5 through a valve seat 8A as shown by arrow P of FIG. 17. Then, the fuel gas is discharged through the canister 7 into an inlet pipe (not shown) or the like.
When the fuel level in the fuel tank 1 becomes high, the fuel-level sensing valve 2 is lifted to close the valve seat 2A, preventing the fuel from being directly fed to the canister 7.
Normally, when the fuel-gas pressure in the fuel tank 1 remains high, the fuel-level sensing valve 2 is fixed to the valve seat 2 A to keep the vent line 5 closed. The pressure in the fuel tank 1 can be reduced by opening the tank pressure control valve 9 provided in the evaporate line 6 to introduce the atmospheric pressure into the fuel tank 1 through the canister 7. As a result, the fuel-level sensing valve 2 drops due to the self-weight, thus opening the vent line 5.
In the case where a vehicle is excessively tilted or overturned, a large quantity of fuel in the fuel tank 1 may possibly flow out through the evaporate line 6 into the canister 7. The outflow of the fuel may be prevented by the fuel cut valve 3 that lifts up to close a valve seat 3A.
Hereinafter, a fuel evaporative emission controller of another related art will be described with reference to FIG. 18.
Like elements are denoted with like reference numerals and codes, and description thereof will be omitted.
In the fuel evaporative emission controller of FIG. 18, the fuel cut valve 3 is provided separately from the valve structure 4.
This controller has problems as described below.
First, since the vent line 5 and evaporate line 6 are connected to the canister 7 through the piping such as rubber hoses, a long assembling time is required, and the cost is increased because of additional parts such as rubber hoses.
Moreover, due to the strict regulation on evaporative emission in recent years, permeation of the fuel gas through the valves and piping such as rubber hoses has become a major concern.
Accordingly, it is not preferable to arrange the complex piping and to form a large opening in the fuel tank in terms of escape of the fuel gas.
Moreover, in the above-mentioned controller, the fuel-level sensing valve 2, fuel cut valve 3 and pressure sensor 10 are mounted to the upper wall of the fuel tank by means of a rubber O-ring 11 and the like. Therefore, the evaporation gas permeates through the O-ring 11 into the outside.
It is one object of the invention to provide a fuel evaporative emission controller that simplifies piping mount, achieves cost reduction by minimizing piping like rubber hoses, and reduces the fuel gas permeation.
In order to achieve this object, the fuel evaporative emission controller of the invention includes a valve structure having at least a fuel-level sensing valve and a first fuel cut valve. The valve structure also includes a vent line provided in the valve structure and an evaporate line provided in the valve structure. The vent line and the evaporate line is communicated with each other within the valve structure.
Since the piping like rubber hoses and the number of joints can be minimized, the assembling time as well as the cost for providing the rubber hoses and the like can be reduced.